The invention is directed to an automatic locking device for double hung windows with removable sashes.
Double hung windows conventionally include a pair of vertically slidable window closures or sashes each of which is smaller than the rectangular window opening, but which together slide into an overlapping position in which the window opening is closed. Both sashes are slidable to open the window to varying degrees.
Each sash also conventionally slides relative to a pair of jamb liners that are installed on opposite sides of the window jamb, and which retain as well as slidably guide both sashes. Jamb liners are typically extruded from a plastic material that provides a relatively low frictional sliding surface and which remains relatively stable over a broad range of temperatures. The jamb liner may include some type of spring or biasing mechanism between the back side of the liner and the jamb side that urges the jamb liner into retaining contact with the side of the associated sash. See, for example, U.S. Pat. No. 5,265,308 issued Nov. 30, 1993 to Michael M. May.
Double hung windows also typically include some type of balance mechanism on each side, generally within the jamb liner itself, that counter balances the weight of the sash and enables it to be retained in a desired position. Generally, the balancing mechanism, which often comprises a coil spring, is connected to a force transfer device that is slidably disposed within a vertical channel within the jamb liner and which is also connected to the sash. The force transfer device may be constructed to frictionally slide within the jamb liner to assist in the overall balance of the sliding sashes, in which case it is referred to as a friction clutch or brake shoe. The sash typically includes a laterally projecting pin on each of its sides, and the pin projects into the jamb liner channel to mechanically interconnect with the brake shoe. As assembled, the sash, by virtue of its weight, exerts a downward force on the brake shoe, and the balance mechanism exerts an upward force on the brake shoe to maintain the sash in a desired position as well as to permit a smooth, counter balanced movement from position to position. The brake shoe may include an adjustment to vary the degree of friction with which it slides within the jamb liner to accomplish the desired balance.
Virtually all currently manufactured double hung windows are also constructed to permit the home owner to remove both sashes to gain access to the external glass panes for simplified cleaning. To accomplish this, the sash is laterally forced against one side of the associated jamb liner, which enables clearance and removal of the opposite side from its associated jamb liner. The sash may then be withdrawn from the window opening.
However, for many windows having removable sashes, a mechanism is provided to lock the brake shoes into a fixed position within the liner when the sash is removed since there is no longer a downward force on the brake shoe to counter balance the upward force of the balancing mechanism. In other words, unless the brake shoe is locked in place, it will immediately be pulled by the coil spring to the uppermost position within the jamb liner channel. This may damage the head jamb, the balance mechanism and/or the brake shoe and in any case leaves the brake shoe in an improper position (and perhaps inaccessible) for reinstallation of the sashes.
There are many automatically locking brake shoes currently available. One of the more popular locking brake shoes permits sash removal by tilting the sash inwardly from its top edge, pivoting relative to the bottom edge. This enables easy access to the outside surfaces of the glass panes within the sash for convenient cleaning. As the sash is tilted inward, it also rotates a mechanism within the brake shoe that causes a locking member to engage the channel sides of the jamb liner and retain the brake shoe in place. Such devices operate satisfactorily, although they typically require the sash to be tilted to a predetermined point before the locking mechanism is actuated, and this can be difficult to operate if the home owner does not understand the function and structure of the device. Further, the sash often must be precisely aligned with the brake shoe members on each side upon reinsertion, and it is sometimes difficult to accomplish this precise alignment simultaneously with both brake shoes.
Most conventional locking mechanisms also interact with the sash and/or balance mechanism in a specific manner which means that the brake shoe cannot be adapted to different sashes and/or different balance mechanisms. A brake shoe having more universal application would effect reductions in cost in a number of ways, including but not limited to manufacture, inventory, repair and replacement.
Another problem with conventional brake shoes having an automatic locking feature is that the locking feature may be actuated by the upward pull of the balance mechanism when the sash is removed. A problem created by such structural arrangements is that the balance mechanism is conventionally a coil spring, the force of which varies as a function of its displacement. As the sash is moved upwardly in its guided channel, the spring force decreases because the spring is stretched to a lesser degree. If this force diminishes to the point that it is less in magnitude than the resisting frictional force, the locking feature may not be actuated when the sash is fully tilted or removed.
The inventive counter balance mechanism, or brake shoe, was developed with the objective of overcoming these disadvantages. The inventive brake shoe consists of a two piece member, the first of which is a member that is slidably disposed in an associated jamb liner channel and which is adapted for connection to the counter balance coil spring. Preferably, the first member includes adjustment means for varying the degree of friction it has with the jamb liner channel.
The second member is pivotally connected to the first member and movable between a sliding position in which it does not engage the jamb liner channel side and a locking position in which a biting or locking edge rotates into locking engagement with the channel side. The second member is normally rotated into the locking position by a separate and independent locking spring. The second member is forced into its sliding position by the interlocking engagement of a sash pin carried by the sash side. The sash pin uniquely engages the brake shoe in a manner in which it seats in an interlocked position with the sash slidably disposed between the jamb liners, but in which it may be rotated out of this interlocked position when the sash is tilted inward. As soon as the sash begins inward tilting movement, the independent locking spring causes the second member to rotate relative to the first member to engage the jamb channel side and lock the brake shoe into place.
The inventive brake shoe solves a number of the problems encountered in prior art devices. The fact that it has an independently operating spring means that the locking mechanism will be fully actuated whether the sash is in a lower or upper position within the jamb. In either case, the force of the locking spring immediately initiates the locking mechanism as soon as the sash begins to be tilted inward. This occurs even if the sash is in an upper position and the coil spring of the balance mechanism generates very little force.
The independently operated locking spring also enables the brake shoe to be used in windows that vary in size, and to work effectively in windows of all sizes.
Further, because of the unique relationship of the sash pin to the brake shoe, the device operates effectively with a significant degree of forgiveness. For example, if for some reason the sash is removed in such a way that one side leaves its jamb liner at a different point than the opposite side, the brake shoes will nevertheless properly lock. Conversely, there is no particular alignment necessary on the part of the sash pins with the respective brake shoes. Because of the unique construction and operation of the brake shoe, the sash pin may enter the brake shoe either as the window is tilted back into position or as the sash pin engages the brake shoe by vertically sliding from above. This will be accomplished even though the brake shoes on each side of the jamb lock at different elevations within the jamb liner.
Further, the inventive brake shoe includes an interlocking feature that prevents the sash pin from being vertically raised once it has been interlockably seated. This means that the sash pin will not become separated from the brake shoe during any phase of sliding operation of the sash.
The invention will be more fully appreciated from the appended drawings and the following description.